A three-phase alternator rectifier bridge, such as used in a motor vehicle alternator, comprises three "negative" diodes having their anodes connected to a ground terminal and three "positive" diodes having their cathodes connected to a voltage output terminal. Each of the cathodes of the negative diodes are connected to one of the anodes of the three positive diodes and to one of three stator windings of an alternator. The diodes used to form rectifier bridge circuits have been packaged together as a unit which preferably is mounted within the housing of the alternator. For example, U.S. Pat. No. 3,184,625 describes a technique for mounting diodes on metal plates within the housing of an alternator but requiring numerous wire-to-wire solder connections to interconnect the diodes in the rectifier unit.
A problem created and addressed in known prior art rectifier bridge circuits is the dissipation of heat which is generated by the conduction of substantial currents through the diodes of the bridge circuits. U.S. Pat. Nos. 3,539,850, 3,925,809, 3,959,676, 4,218,694, 4,307,437, 4,321,664, 4,538,169, 4,799,309 and 4,835,427 all show various techniques for packaging diodes in a manner that will facilitate heat dissipation.
My previous U.S. Pat. No. 5,043,614, discloses a method and structure for assembling an alternator rectifier bridge incorporated into an alternator housing. Half of the diodes of the rectifier bridge are inserted into apertures formed into an alternator housing end plate such that the end plate serves as one output for the alternator and also as a massive heat sink to dissipate heat generated in the diodes. Typically, the diodes inserted into the end plate are negative diodes with their anode electrodes being inserted and their cathode electrodes extending beyond the end plate. The other half of the diodes of the rectifier bridge are inserted into apertures formed in a radiator plate. Typically, the diodes inserted into the radiator plate are positive diodes with their cathode electrodes being inserted and their anode electrodes extending beyond the radiator plate. The radiator plate is embedded into a plastic circuit member together with conductor members which serve to interconnect electrodes of the diodes and connect the diodes to stator windings of the alternator. The conductor members also provide other electrical connections required for efficient manufacture and proper operation of the alternator.
Although the patented radiator plate has improved heat dissipation abilities over previously known multiple component bridge circuit assemblies, the terminals formed with the radiator plate for connection as an output terminal to a conductor were formed as spade terminals. However, the connection between the fork-shaped female terminal which dovetails with the spade-shaped male terminal has limited current carrying capability. Moreover, modern vehicles have more load circuits, and alternators are accordingly built to produce substantially higher currents. Furthermore, the clamping force of the female member must be limited to allow insertion of the spade shaped male terminal. Any looseness in the connection increases the resistance of the terminal, and in view of the high current flowing from the alternator, substantially increases the heat generated at the coupling. Moreover, the more heat generated at the coupling, the higher the resistance of the connection. As a result, an ever increasing cycle or runaway of increasing heat and resistance can adversely affect the electrical system and the coupling.
Previously known couplings which provide a secure connection between mating parts often employed a threaded fastener specially constructed for mounting and threadably engaging electrical terminals against each other. However, while such a fastener carries higher clamp loads, and therefore can carry higher currents, such structures are difficult to manufacture, install and assemble, and can employ numerous component parts such as insulating shells and machined supports. One previously known connection included a bolt extending through a plastic insulating sleeve inserted through an alternator housing portion. A first nut tightened against the end of the sleeve supported the harness eyelet for engagement by a second nut threadedly engaged on the bolt against the eyelet and the first nut. However, the effect of changing temperature, aging and environmental conditions on the different materials could cause loosening of the electrical connection as the nuts separated.
Another previously known alternator construction with end plates supporting a rectifier bridge assembly required a specially constructed bolt mounted for contact with the positive diode plate by a knurled peripheral portion in wedging engagement to the plate, and a threaded portion for threadably engaging a nut. In addition, a threaded boss area extended through an insulating housing to engage a boss with a flared flange retaining a washer on the boss. The boss was threadably engaged with the bolt once the knurled portion had been embedded in the rectifier assembly to provide a flat surface against which terminals and a nut could be tightly engaged to complete a secure connection for output from the alternator. However, the manufacturing and assembly difficulties render the alternator construction very expensive. Since other previously known bolt and nut connections, may not be efficient conductors. Previous practice required the bolt to be fabricated of more expensive material with better conductivity, such as a copper stud, which is required to be larger for strength. Furthermore, the loose connection problems discussed above could be encountered with such a structure.